A corporation, by strict legal definition, is any group of people acting as if one for whatever their stated purpose. This definition is broad enough to include non-profits or NGOs. In practical terms, however, it refers to a an organization which makes something and hires people to do it.
But what is the purpose of them? Recently, it’s become very popular to assume that the main purpose of a corporation is to maximize shareholder value. That is, to grow and reward those who put their money down to make it all happen in the first place.
There are many reasons to see this need for constant growth as dangerous. Most generally, it’s not sustainable outside of the rate of population increase and productivity gains, at least once the entire planet reaches a similar level of development. But more important, the view of what a corporations is, or at least why it exists, is extremely damaging to its own stated purpose. And it’s easily shown to not actually be true in practice.